The present invention relates to a check system for checking information indicative of connections in a multistage switching network. In particular, the present invention relates to a check system for checking connection logistics between an output terminal of a switching section in one stage and an input terminal of an associated switching section in the next adjacent stage, for all connection paths in a multistage switching network which comprises two or more stages of switching groups each including two or more switching sections.
An example of a multistage switching network is described in conjunction with a three-stage switching network. A switching size is indicated by M by N (M.times.N) when the three-stage switching network has M input lines and N output lines (where M and N are each a natural number). The three-stage switching network includes the three stages of switching groups. The switching group in the first stage comprises P switching sections (where P is a natural number represented by M/m). Each of the P switching sections has a switching size of m by r (m.times.r) that is defined by m input lines and r output lines (where m and r are each a natural number, and m.ltoreq.M). The switching group in the second stage comprises R switching sections each having a switching size of p by q (p.times.q) that is defined by p input lines and q output lines. Likewise, the switching group in the third stage comprises Q switching sections (where Q is a natural number represented by N/n) having a switching size of r by n (r.times.n) that is defined by r input lines and n output lines. The three-stage switching network further comprises a main control section. The main control section controls connections between the individual switching sections of the first, the second, and the third switching groups. In addition, the main control section comprises a memory unit for use in storing information indicative of the connections between the individual switching sections of the first, the second, and the third switching groups.
Each switching section in the switching groups comprises a switching unit and a switch control unit. The switching unit has a plurality of input terminals and a plurality of output terminals and is adapted to connect one of the input terminals to one of the output terminals. The switch control unit controls the switching unit.
The following problems arise in such a multistage switching network if no checking is made about whether the information indicative of the connections between the switching sections stored in the memory unit is logically correct.
The main control section of the conventional multistage switching networks searches an available path for the connection according to the information indicative of the connections that is stored in the memory unit. Such operation is made even though a portion of the information is incorrect, when the main control section receives a request for establishing a connection between the input and the output terminals in the multistage stage switching network. The output terminal already occupied may be allocated to other path. This means the path which is already established for the individual switching sections may be disconnected when there is a request for establishing a connection between the input and the output terminals in the multistage switching network with a portion of the information indicative of the connections being damaged in the memory unit.
In addition, the conventional multistage switching networks may download a command for connection into the individual switching sections that is different from the actual status of connection between the switching sections established according to the incorrect information stored in the memory unit. This may result in establishment of a path that is different from the one already established.
The main control section is connected to the individual switch control units in the switching sections via control signal lines. The control signal lines may be disconnected or the switch control unit in the switching sections may be reset. If such disconnection or reset happens, the information indicative of the connections in the memory unit is downloaded into the individual switching sections after recovery of the connection. The downloading is made in order to match the connection status with the connection indicated by the information in the memory unit of the main control section. The path that is already established between the individual switching sections may be disconnected when the downloading is made with a portion of or entire the information indicative of the connections is damaged in the memory unit.
Therefore, an object of the present invention is to provide a check system for checking information indicative of connections in a multistage switching network, in which the checking system is capable of checking whether the information is damaged that is stored in a memory unit and is indicative of connections in the multistage switching network to avoid accidental disconnection of the path that is already established between individual switching sections due to incorrect information about the connections.